The present invention relates to linear transmission devices, and relates more particularly to a photoelectric control structure for a linear transmission device which comprises a mount, a transmission gear mounted on the mount and coupled to a motor, a photoelectric circuit board mounted on the mount and having a phototransistor and an infrared light emitting diode controlling by the phototransistor, a light chopper turned by the transmission gear to intermittently block light from the light emitting diode toward, and a chopper cover fastened to the mount and covering the light chopper and the photoelectric circuit board for protection, wherein when the motor is started, the transmission gear is driven to turn the light chopper, causing light to intermittently pass through to the phototransistor, and therefore the infrared light emitting diode intermittently drives the phototransistor to send a pulse wave signal to the signal input terminal of a satellite antenna allocator.
FIG. 3 shows a regular linear transmission device which comprises a mount 11 having a recess 12 at a suitable location, a solenoid switch 14 mounted within the recess 12, a retainer plate 16 disposed adjacent to the recess 12 to hold the solenoid switch 14 in place, and a multipolar magnet 15 disposed adjacent to the solenoid switch 14 and turned by a transmission gear (not shown). When the solenoid switch 14 is in alignment with the S or N pole at the periphery of the multipolar magnet 15, it is attracted and switched on; when the solenoid switch 14 is in alignment with non-polarity portion at the periphery of the multipolar magnet 15, it is switched off. Because this structure of a linear transmission device is of the mechanical transmission type, the mechanical mechanism wears quickly with use, causing the transmission accuracy of the device to be affected.